“We are pushing this material to UK media channels, eg a BBC radio programme exposing tensions between AQ leadership and supporters. And a restricted working group will communicate niche messages through media and non-media.”

It’s difficult not to wonder at times about the provenance of some anonymous comments left on internet discussion sites such as the BBC’s “Have Your Say” and the Guardian’s “Comment is Free”. ‘Astro-turfing’ seems almost impossible to prevent in such circumstances, and for anyone with a vested interest in promoting a particular point of view, the temptation must be difficult to resist.

Now the Guardian reports that a UK government counter-terrorism unit is targeting media organisations “as part of a new global propaganda push designed to ‘taint the al-Qaida brand'”. A strategy document recommends that the authorities “channel messages through volunteers in internet forums”.

“We are pushing this material to UK media channels, eg a BBC radio programme exposing tensions between AQ leadership and supporters”, says the leaked document. “And a restricted working group will communicate niche messages through media and non-media.”

While it isn’t hard to understand the rationale for tackling Al Qaeda in this way (and it’s surely preferable to torturing people), the most obvious fear is that those who begin disseminating misinformation for the ‘greater good’ may soon find themselves on a slippery slope. If ‘astroturfing’ to discredit a hostile terror group is acceptable, why not a hostile foreign government? And if spreading misinformation in defence of UK security interests is acceptable, why not our economic interests, which are, arguably, ultimately tied up with our security? Or in defence of an unpopular government policy which ministers feel is essential for the good of the country?